The instant invention relates to a gear system which utilizes a planetary gear train to provide a pair of rotary outputs from a single rotary input. More specifically, the instant invention is directed to a gear system for driving a pair of similarly loaded output shafts with a single rotary input, as where a pair of like helicopter rotors are to be driven with equal torque at approximately the same speed by a single power plant.
Planetary gear trains are known both for their compact size and their ability to produce a constant torque output of varying rotational speed from a first rotary input through the use of a second, controlling input. More specifically, typical planetary gear trains comprise three members rotatable about a common axis, those members being a sun gear, an annulus gear, and a planetary gear carrier. The planetary gear carrier supports a plurality of planetary gears, each of which meshes with both the sun and annulus gear of the gear train. Two of the members, e.g., the sun and annulus gears, are driven or otherwise controlled by the two rotary inputs to the gear train. The remaining gear train member, e.g., the planetary gear carrier, rotates at a speed and in a direction dictated by the rotational speed and direction of the two inputs, thus providing the lone output from the gear train. It is noted that, in this respect, one of the inputs frequently comprises a fixed, non-rotating input, or a variable-speed input, as may be obtained, for example, by connecting a brake or clutch to one of the input members.
Unfortunately, the prior art fails to teach a gear system which incorporates the advantages of planetary gear trains while providing a pair of rotary outputs from a single rotary input.